1. Field of the Invention
The present invention relates to an image processing, and more particularly, to a method and apparatus for determining whether an image is a shaken image by using auto focusing.
2. Description of the Related Art
In general, an optical digital system (camera) uses an auto focusing (AF) function to automatically adjust a focus on a certain subject. In addition, most compact digital cameras use through the lens (TTL) contrast detection to precisely fine tune and define a subject. Such compact digital cameras do not have a separate AF sensor, and adjust focus by analyzing the contrast of an image obtained via a charge coupled device (CCD)/complementary metal oxide semiconductor (CMOS) image sensor.
A conventional method of adjusting focus of a photographing lens of a digital camera includes generating an image signal by photoelectric-transformation of an image of a subject using an image pickup device such as a CCD, calculating an AF evaluation value, which is a contrast value of an image, by extracting a high frequency component from an image signal in a predetermined AF area of a captured image, and detecting a focus location of the photographing lens based on the AF evaluation value. According to this method, the AF evaluation value is calculated from each focus location of a focus lens while moving the focus lens along an optical axis direction, and a location having the maximum AF evaluation value is detected as the focus location. The AF evaluation value is obtained by filtering a brightness component using a high pass filter (HPF) and integrating the obtained result.
Meanwhile, users select high quality images from a lot of images stored in a digital camera, check the selected images, and upload the selected images to web servers. Users also delete low quality images, e.g., shaken images, when searching for images using a playback device or a computer.
Shaken images may be generated due to various reasons such as motion of a subject when an image of the subject is captured, long exposure time at night or indoor photographing, hand tremble of a user when pressing a shutter button, or motion of the digital camera. Thus, it is not easy to individually select shaken images from among many images stored in the digital camera and delete them.